Thermocline

The thermocline is the transition layer in a body of water between the warm, well-mixed surface water and the cold, stagnant deep water. In the ocean, the thermocline typically spans depths from 200 to 1000 meters, with its depth and sharpness varying by latitude and season. The thermocline acts as a thermal barrier that inhibits vertical mixing, and its depth fluctuations are the ocean's primary memory mechanism in climate oscillations such as the El Niño-Southern Oscillation and the Pacific Decadal Oscillation. From a systems perspective, the thermocline is the capacitor of the coupled ocean-atmosphere system.